1. FIELD OF THE INVENTION
The present invention relates to a disc unit and more particularly to a disc unit suitable for a magnetic disc unit or an optical disc unit such as a laser disc or compact video disc unit in which a recording/reproducing head slidably contacts disc as a recording medium so that information is recorded on or reproduced from the disc.
2. DESCRIPTION OF THE PRIOR ART
There have been proposed a disc unit such as a magnetic disc unit of the type having an automatic loading mechanism so that a magnetic disc inserted through an insertion slot into the magnetic unit is automatically transferred to its operative position where information is recorded on or reproduced from the magnetic disc by a magnetic head and then is securely clamped in position. After the recording or reproducing, the magnetic disc is automatically released from its clamping condition and discharged through the insertion slot from the magnetic unit.
The magnetic disc unit of the type described is provided with two separate drive means. One drive means is used to transport a magnetic disc from the insertion slot to the operative position, while the other drive means is used to clamp the magnetic disc to a driving mechanism for rotating the magnetic disc.
A conventional magnetic disc unit with two independent drive means as described above will be described in detail with reference to FIGS. 1 and 2.
In FIG. 1, showing the block diagram of the magnetic disc unit, to the inputs of a control unit 1, connected are magnetic disc insertion detection means or first detection means 2, second detection means 3 for detecting whether or not a magnetic disc has been transferred to its operative position, third detection means 4 for detecting whether or not a clamping mechanism has been returned to its initial position, fourth detection means 5 for detecting whether or not the clamp of the magnetic disc is completed and a magnetic disc discharge switch 6 for instructing the discharge of the magnetic disc.
One of the outputs of the control unit 1 is connected to a first motor drive circuit 7 which in turn is connected to a first motor 8 which is coupled to a mechanism 9 for transporting the magnetic disc. Therefore, in response to the output signal from the control unit 1, the first motor drive circuit 7 is activated so as to drive the first motor 8, whereby the magnetic disc is transported by the mechanism 9.
The other one of the outputs of the control unit 1 is connected to a second motor drive circuit 10 which in turn is connected to a second motor 11 which is coupled to a clamping mechanism 12. Therefore, in response to the output signal from the control unit 1, the second motor drive circuit 10 is activated so as to drive the second motor 11, whereby the clamping mechanism 12 is actuated.
In a timing chart shown in FIG. 2 to explain the operations of the conventional magnetic disc unit of the type described above with reference to FIG. 1, reference numeral 2s designates an output signal derived from the first detection means; 3s, an output signal derived from the second detection means; 4s, an output signal derived from the third detection means; 5s, an output signal derived from the fourth detection means; 6s, an output signal derived from the magnetic disc discharge switch 6; 8s, a signal for driving the first motor 8; and 11s, a signal for driving the second motor 11.
When a magnetic disc is inserted into the magnetic disc unit, this insertion is detected by the first detection means 2, so that the output signal 2s is obtained and simultaneously the first motor 8 is driven to rotate in the clockwise direction or in one direction.
As a consequence, the inserted magnetic disc is transported through the magnetic disc unit to its operative position. When the transfer of the magnetic disc is completed, the second detection means 3 generates the output signal 3s. In response to this signal 3s, the first motor 8 stops its rotation. At the same time, the second motor 11 is driven to rotate, so that the magnetic disc is clamped. When the magnetic disc is clamped, the fourth detection means 5 generates the signal 5s. In response to this signal 5s, the second motor 11 stops its rotation. Thus, the magnetic disc is securely clamped at its operative position.
Thereafter, information is recorded on or reproduced from the magnetic disc in a manner well known in the art. When the recording or reproducing operation is completed, the magnetic disc discharge switch 6 is depressed so that the signal 6s is generated. In response to this signal 6s, the second motor 11 is driven to rotate in the counterclockwise direction or in the other direction, so that the magnetic disc is released from its clamping condition and consequently the clamping mechanism has returned to its initial position.
Then, the third detection means 4 generates the signal 4s. In response to this signal 4s, the second motor 11 stops its rotation. At the same time, the first motor 8 is driven to rotate in the counterclockwise direction or the other direction, so that the magnetic disc is discharged from the magnetic disc unit.
When the magnetic disc is discharged, the output signal 2s from the first detection means 2 is turned off or becomes a low level, so that the first motor 8 stops its rotation. That is, the operation for discharging the magnetic disc from the magnetic disc unit is completed.
In such a conventional magnetic disc unit as described above, the two motors 8 and 11 are used, so that the control circuit as well as control timings are complicated. In addition, a relatively large number of component parts are required, so that the magnetic disc unit is large in size and heavy in weight.
Furthermore, in the conventional magnetic disc unit of the type described above, the magnetic disc is not easily discharged from the magnetic disc unit once it is inserted, even when the malfunction of the automatic loading or discharging mechanism occurs. As a result, in order to take the magnetic disc out of the magnetic disc unit, there is no way but to remove a cover or some portion of the unit.
Moreover, the conventional magnetic disc unit of the type described above is not provided with means for notifying an operator whether or not a magnetic disc has been already loaded into the magnetic disc unit. As a result, erroneous operations resulting from the loading of the magnetic disc is not prevented.